When all was quiet, Courtney rushed toward her brother and her friend, hugging them tightly. "Where were you?" she asked. "I was so worried."

"We were in Paris with Madame Curie. What about you? We looked everywhere," said Morgan.

"What's wrong?" Morgan asked.

"I was so worried, I didn't think to bring anything back. I don't have any puzzle piece."

"We brought back some pitchblende from Madame Curie's lab," Collin told her proudly. "That's a type of rock, you know? We put it in the puzzle piece and it closed up, but we didn't know what the riddle was."

"Pitchblende?" said Courtney in an awed voice. She looked down at her hand. In her tightly clenched fist she still held the small rock paperweight that Einstein had handed her in his office.
"You brought pitchblende back, too?" asked Morgan, surprised.